Prior art asphalt emulsions used to produce graded and dense graded paving mixtures (ASTM D 3628) fall into two classifications: (1) Medium Setting (“MS”) (HFMS-2S and CMS-2S, each of which must contain petroleum distillate; and (2) Slow setting (“SS”) (SS-1, SS-1H, CSS-1 and CSS-1H. The Medium Setting (MS-types) require the use of significant amounts of petroleum distillate solvents to reduce the viscosity of the emulsion residue to aid in the coating of the aggregate, since the emulsion breaks down early in the mixing process with relatively high surface area aggregates (those containing significant quantities of fine aggregate). This solvent must be of a distillate type to prevent the resulting binder from being too soft to fulfill its intended purpose, that of a bituminous binder for the mixture. These solvents are not only expensive, they are also a waste of energy and detrimental to the environment when they evaporate, which typically can take up to several days or longer. The Slow Setting (SS-types) are required to be very stable so that mixing (dispersion of the emulsion) can take place prior to the emulsion breaking down. These mixtures are susceptible to wash off in times of rain, which is environmentally not acceptable, and construction problems often are caused by the mixture being too tender, since the residue can still be in an emulsified state and not act as the intended bituminous binder.
The Rapid Setting (“RS”) type of materials break down much faster than the MS-types, thus they are not suitably used in mixtures, especially graded and dense graded paving mixtures. HFRS-2, though sometimes made with reacted tall oil tall, oil pitch, or tall derivatives) added to the asphalt cement prior to being emulsified, is still a rapid setting emulsion (demulsibility 60% or greater) and will not produce satisfactory mixtures that retain their integrity sufficient to be used for many types of paving applications.
For example, U.S. Pat. No. 4,433,084 discloses a high-float, rapid-setting emulsion of asphalt, tall oil, tall oil derivatives, or mixtures thereof, a copolymer of styrene butadiene styrene and styrene-isoprene-styrene blocks, petroleum distillate, water, and a strong base. These rapid setting materials are disclosed for use primarily in surface treatments such as chip seal coats, as well as penetration treatment of macadam, and as sand seal coats and tack coats to promote adhesion of overlayers.
U.S. Pat. No. 5,221,703 discloses modified asphalt cements including asphalt cement, reacted tall oil, tall oil pitch, tall oil derivatives or mixtures of these, and polymers selected from block copolymers and latexes, both synthetic and natural, as well as methods of manufacturing the same by blending a reacted tall oil-modified asphalt cement with a polymer-modified asphalt cement to obtain the desired properties, modifying an asphalt cement with a reacted tall oil, tall oil pitch, tall oil derivatives or mixture thereof, and then adding the selected polymer(s) to this tall oil-modified asphalt cement, modifying the asphalt cement with the selected polymer(s) and then adding the tall oil, tall oil pitch, tall oil derivatives and mixtures thereof and reacting with a strong base, and, adding the polymer(s), tall oil, tall oil pitch, tall oil derivatives and mixture thereof and the strong base all to the asphalt cement at or nearly at the same time.
U.S. Pat. No. 4,362,568 discloses a petroleum distillate-free or essentially petroleum distillate-free prime coat material for application to absorptive surfaces, such as untreated road or street surfaces, which is designed to penetrate, bond, and stabilize such existing surfaces and to promote adhesion between such surfaces and construction courses that follow. This type of material is also often used as a dust palliative, such as being applied to an untreated surface to control dust.
Thus, it is desired to obtain more environmentally friendly graded and dense graded paving mixtures suitably used in medium setting or slow setting materials that can provide a suitable lifespan to the resultant application, e.g., a road or other paved or coated surface.